Parati Mattia, Clarke Louisa, Anderson Paul, Hill Robert, Khalil Ibrahim, Tchuenbou-Magaia Fideline, Stanley Michele S, McGee Donal, Mendrek Barbara, Kowalczuk Marek, Radecka Iza
Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton WV1 1 LY, UK.
Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AD, UK.
Polymers (Basel). 2022 Jul 20;14(14):2937. doi: 10.3390/polym14142937.
Poly-γ-glutamic acid (γ-PGA) is a bio-derived water-soluble, edible, non-immunogenic nylon-like polymer with the biochemical characteristics of a polypeptide. This Bacillus-derived material has great potential for a wide range of applications, from bioremediation to tunable drug delivery systems. In the context of oral care, γ-PGA holds great promise in enamel demineralisation prevention. The salivary protein statherin has previously been shown to protect tooth enamel from acid dissolution and act as a reservoir for free calcium ions within oral cavities. Its superb enamel-binding capacity is attributed to the L-glutamic acid residues of this 5380 Da protein. In this study, γ-PGA was successfully synthesised from Bacillus subtilis natto cultivated on supplemented algae media and standard commercial media. The polymers obtained were tested for their potential to inhibit demineralisation of hydroxyapatite (HAp) when exposed to caries simulating acidic conditions. Formulations presenting 0.1, 0.25, 0.5, 0.75, 1, 2, 3 and 4% (w/v) γ-PGA concentration were assessed to determine the optimal conditions. Our data suggests that both the concentration and the molar mass of the γ-PGA were significant in enamel protection (p = 0.028 and p < 0.01 respectively). Ion Selective Electrode, combined with Fourier Transform Infra-Red studies, were employed to quantify enamel protection capacity of γ-PGA. All concentrations tested showed an inhibitory effect on the dissolution rate of calcium ions from hydroxyapatite, with 1% (wt) and 2% (wt) concentrations being the most effective. The impact of the average molar mass (M) on enamel dissolution was also investigated by employing commercial 66 kDa, 166 kDa, 440 kDa and 520 kDa γ-PGA fractions. All γ-PGA solutions adhered to the surface of HAp with evidence that this remained after 60 min of continuous acidic challenge. Inductively Coupled Plasma analysis showed a significant abundance of calcium ions associated with γ-PGA, which suggests that this material could also act as a responsive calcium delivery system. We have concluded that all γ-PGA samples tested (commercial and algae derived) display enamel protection capacity regardless of their concentration or average molar mass. However, we believe that γ-PGA D/L ratios might affect the binding more than its molar mass.
聚γ-谷氨酸（γ-PGA）是一种生物衍生的水溶性、可食用、非免疫原性的类似尼龙的聚合物，具有多肽的生化特性。这种源自芽孢杆菌的材料在从生物修复到可调药物递送系统等广泛应用中具有巨大潜力。在口腔护理方面，γ-PGA在预防牙釉质脱矿方面具有很大前景。唾液蛋白statherin先前已被证明可保护牙釉质免受酸溶解，并作为口腔内游离钙离子的储存库。其出色的牙釉质结合能力归因于这种5380 Da蛋白质的L-谷氨酸残基。在本研究中，γ-PGA是由在添加藻类培养基和标准商业培养基上培养的纳豆芽孢杆菌成功合成的。对获得的聚合物在模拟龋齿酸性条件下抑制羟基磷灰石（HAp）脱矿的潜力进行了测试。评估了呈现0.1%、0.25%、0.5%、0.75%、1%、2%、3%和4%（w/v）γ-PGA浓度的制剂，以确定最佳条件。我们的数据表明，γ-PGA的浓度和摩尔质量在牙釉质保护方面均具有显著意义（分别为p = 0.028和p < 0.01）。采用离子选择性电极结合傅里叶变换红外研究来量化γ-PGA的牙釉质保护能力。所有测试浓度均对羟基磷灰石中钙离子的溶解速率显示出抑制作用，其中1%（wt）和2%（wt）浓度最为有效。还通过使用商业66 kDa、166 kDa、440 kDa和520 kDa的γ-PGA级分研究了平均摩尔质量（M）对牙釉质溶解的影响。所有γ-PGA溶液都附着在HAp表面，有证据表明在持续酸性挑战60分钟后这种附着仍然存在。电感耦合等离子体分析显示与γ-PGA相关的钙离子大量存在，这表明这种材料也可以作为一种响应性钙递送系统。我们得出结论，所有测试的γ-PGA样品（商业来源和藻类来源）无论其浓度或平均摩尔质量如何，都具有牙釉质保护能力。然而，我们认为γ-PGA的D/L比可能比其摩尔质量对结合的影响更大。
